Figure 1.

Standard potentials (E°) of various redox proteins and enzymes measured at pH 7.0 and recalculated vs. standard hydrogen electrode (SHE) reference. The potentials spread over range of values for the species originating from different biological sources. The data (except FAD oxidases/dehydrogenases and PQQ dehydrogenases) is adopted from [3] with permission. The potentials of FAD oxidases originate from refs. [7,8]; the potentials of FAD dehydrogenases originate from refs. [9,10,11]; the potentials of PQQ dehydrogenases originate from [12,13,14,15].